Secondary Navigation has vanished on site using 'Dispatch'

Hi

I run a community site built with David's excellent 'Dispatch', along with GeneratePress Premium.

It has functioned and looked good for many months. But now the Secondary Navigation has suddenly disappeared for reasons I cannot work out.

(The SecNav is positioned on the hook generate_before_footer_content, and set to display on the entire site. It has worked well.)

The Customiser still has location set to 'No Navigation', and the hook element is unchanged as:

<div class="second-nav grid-container">
	<?php 
	if ( function_exists( 'generate_secondary_navigation_position' ) ) {
		generate_secondary_navigation_position();
	}
	?>	
</div>

To try to identify the problem, I have deactivated the two plugins added recently, and the code snippets. But the SecNav still doesn't appear.

In Chrome inspector, I can see the container <div class="second-nav grid-container"></div> is still there, immediately below <div class="site-footer"> but there is nothing in it.

I have a recent staging site where it is still visible. On the live site it is missing. I attach links to both.

I am hoping you may be able to guess what has happened, or what I might have done to cause this.

Thank you.